"We have good reason to believe that there's a bombshell in
Donald Trump's taxes," Romney told Fox News host Neil Cavuto on
Wednesday.

Romney continued:

I think there's something there. Either he's not anywhere near as
wealthy as he says he is, or he hasn't been paying the kind of
taxes we would expect him to pay. Or perhaps he hasn't been
giving money to the vets or the disabled, like he's been telling
us he's been doing.

He called on several major Republican presidential
candidates to release their tax returns, but he took
particular aim at Trump.

"Donald Trump and Marco Rubio and Ted Cruz have not shown us
their back taxes," Romney said. "This was an issue on my
campaign."